Inorganic oxide particles are used by adding them for purposes of pigments, ultraviolet light absorbers, fillers of coating materials, inks, resin compositions, cosmetics, and the like. On the surfaces of such inorganic oxide particles, however, hydroxyl groups are present, and therefore, they have low dispersibility in low-polarity solvents such as oils having poor affinity with water, so that there is a problem that aggregation of the particles is liable to occur.
As a means to solve such a problem, the present applicant has studied, for example, a process for producing resin-coated particles using porous silica particles. In patent literature 1, the present applicant has disclosed an emulsion process or a polymerization process.
Further, the present applicant has described, in patent literature 2, a process for producing resin-coated particles by plasma polymerization. Moreover, the present applicant has disclosed, in patent literature 3, a process for producing resin-coated particles by spray drying of scale-like composite particles.
In the case where polymer gel molecules derived from a natural substance are used for cosmetics, a polymer gel solution is used as it is in most cases, and there are instances where the polymer gel molecules are used as organic particles (including an instance where they are used in combination with organic particles), but there are few instances where they are used in combination with inorganic particles. In patent literature 4, it is described that the polymer gel molecules are stirred in the presence of inorganic pigments, micas, clays, other extender pigments or pigments for cosmetics or industry, and metal (Al, Mg, Ca, Zn, Zr or Ti) salts of polymer substances having a carboxyl group and having an acid value of not less than 200, or the metal salts and a hydrophobing agent and then dried to allow the polymer gel molecules to adhere to the pigments.
On the other hand, in patent literature 5, it is described that natural organic component-supported particles, which are obtained by mixing inorganic particles, such as silicic acid-based compound, alumina-based compound or phosphoric acid-based compound, or organic particles, such as cellulose, with a natural organic component selected from catechins, vitamins, tannins, natural moisture retention factors and essential oils derived from plants and then spray-drying the mixture using a spray dryer, are employable as cosmetic materials because they have dispersibility in linseed oil.
In patent literature 6, a production process in which a moisture-absorbing substance is allowed to adhere to a surface of a pigment is disclosed.